JPH08211384A - Polarizer and projection type liquid crystal display device using the same - Google Patents

Abstract

(57) [Summary] [Object] To provide a compact projection type liquid crystal display device which is excellent in reliability by reducing the temperature rise of the incident side polarization plate of a liquid crystal display element by a thin polarizer. [Structure] A polarizer 5 is formed by arranging a number of elongated convex portions each having a right-angled triangular cross-section along the plane of the transparent plate on both sides of a thin transparent plate, and the incident angle of light to the hypotenuse of the convex portion is the Brewster angle. And a plurality of polarizers 5 are stacked. Also,
Illumination device 1, liquid crystal display element 6 that displays an image by transmitting light emitted from illumination device 1, and liquid crystal display element 6
A projection type liquid crystal display device configured by a projection lens 9 for enlarging an image displayed on the screen 10 on a screen 10,
A polarizer 5 is provided between the lighting device 1 and the liquid crystal display element 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a transmissive liquid crystal display element for injecting liquid crystal between a pair of transparent substrates and displaying image information by the electro-optical effect of the liquid crystal as a light valve, and displaying on the liquid crystal display element. The present invention relates to a projection type liquid crystal display device which irradiates an image to be displayed with light from a lighting device and enlarges and displays it on a screen using a projection lens.

[0002]

2. Description of the Related Art Conventionally, a projection type liquid crystal display in which an image formed according to a video signal as a change in optical characteristics of a light valve is irradiated with light from a lighting device and an optical image is projected on a screen by a projection lens. There is a device etc., and as a light valve used for such a projection type liquid crystal display device,
Many proposals have been made using a transmissive liquid crystal display element. Twisted, a typical example of a liquid crystal display device
The structure of a nematic (TN) type liquid crystal display device is such that two liquid crystal cells are formed by injecting liquid crystal between a pair of transparent substrates each having a transparent electrode film, and two polarization directions are different from each other by 90 °. A polarizing plate is arranged. By combining the action of rotating the plane of polarization by the electro-optical effect of liquid crystal and the action of selecting the polarization component of the polarizing plate, the amount of transmitted incident light is controlled to display image information. It is supposed to do.

However, in the prior art, since both the P-polarized light and the S-polarized light emitted from the illumination device are incident on the liquid crystal display element, polarized light different from the transmission axis of the polarizing plate is incident on the incident side polarizing plate of the liquid crystal display element. Since it is absorbed, the temperature of the incident side polarization plate rises. Further, since the liquid crystal cell is arranged near the incident side polarization plate, the temperature of the liquid crystal cell rises remarkably and it becomes difficult to secure reliability.

To solve this problem, JP-A-3-10218
As described in the publication, a polarizing beam splitter or a polarizer in which a plurality of glass plates are made to have Brewster's angle is arranged between an illuminating device and a liquid crystal display element, and an incident side polarization plate of the liquid crystal display element is arranged. There has been proposed a projection type liquid crystal display device in which polarized light different from the transmission axis of the above is hardly incident on the liquid crystal display element.

[0005]

However, the polarization beam splitter and the polarizer in the above-mentioned prior art have a depth equal to or larger than their effective diameter. Therefore, if a polarizing beam splitter or a polarizer in which a plurality of glass plates are arranged at Brewster's angle is arranged between the illuminating device and the liquid crystal display element, the distance between the illuminating device and the liquid crystal display element becomes long and the set of Invites upsizing.

An object of the present invention is to provide a projection type liquid crystal display device in which the set is downsized by a thin polarizer.

[0007]

In order to solve the above-mentioned problems, the polarizer of the present invention comprises a thin transparent plate, and a plurality of elongated convex portions each having a right-angled triangular cross section arranged on both sides of the transparent plate. It was formed so that the incident angle of light with respect to the hypotenuse of the convex portion would be Brewster's angle.

Further, it comprises an illuminating device, a liquid crystal display element for displaying an image by transmitting light emitted from the illuminating device, and a projection lens for enlarging an image displayed on the liquid crystal display element on a screen. In the projection type liquid crystal display device, the polarizer is provided between the illuminating device and the liquid crystal display element.

[0009]

In the polarizer of the present invention, a large number of elongated convex portions each having a right-angled triangular cross section are arranged on both sides of a thin transparent plate, and the incident angle of light with respect to the hypotenuse of the convex portion is Brewster's. Since it is provided so as to form a corner, a part of the S-polarized light of the incident light is reflected by the hypotenuse of the convex portion, and all the P-polarized light is transmitted. The more the plurality of polarizers are stacked, the more the S-polarized light is reflected.

Further, it comprises an illuminating device, a liquid crystal display element for displaying an image by transmitting light emitted from the illuminating device, and a projection lens for enlarging an image displayed on the liquid crystal display element on a screen. In the projection type liquid crystal display device, by providing a polarizer between the illuminating device and the liquid crystal display element, the light beam emitted from the illuminating device is only the P-polarized light required by the polarizer before entering the incident side polarizing plate. Most of the unwanted S-polarized light that is taken out is reflected. The incident-side polarization plate of the liquid crystal panel is arranged in the direction in which the P-polarized light is transmitted, and unnecessary S-polarized light does not enter the incident-side polarization plate, so that the temperature of the incident-side polarization plate hardly rises.

[0011]

FIG. 1 is a block diagram showing a projection type liquid crystal display device as an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a lighting device, which is a light source 2 such as a metal halide lamp or a halogen lamp and a light source 2.
It is composed of a reflector 3 for reflecting the light beam emitted from the device and irradiating the liquid crystal display element 6. Reference numeral 4 is a cold filter for reflecting and removing infrared rays and ultraviolet rays of light rays, and transmitting only visible light rays.

Numeral 5 denotes S of the light beam emitted from the cold filter 4.
It is a polarizer for reflecting polarized light. Reference numeral 6 denotes a liquid crystal display element, which is composed of deflecting plates 7 arranged on both sides of the liquid crystal cell 8. Reference numeral 9 is a projection lens for enlarging and projecting a display image on the liquid crystal display element 6, and 10 is a screen.

A drive circuit for the liquid crystal display element 6, for example, the circuit block shown in FIG. 1, 11 is a video chroma processing circuit, 12 is an RGB output circuit, 13 is an X driver, 1
Reference numeral 4 is a synchronous processing circuit, 15 is a controller, and 16 is a Y driver.

In this configuration, the light source 5 is the reflector 6
The light emitted from the light source 5 is reflected by the reflector 6 and is disposed near the first focal point position of the cold filter 7
The liquid crystal display element 6 is irradiated with light through.

The image displayed on the liquid crystal display element 6 is magnified by the projection lens 9, and as a result, the magnified image is obtained on the screen 10.

A video input input from a laser disk, VTR or the like (not shown) is processed by the video chroma processing circuit 11 and then input to the RGB output circuit 12. Since the RGB output circuit 12 drives the video signals corresponding to R, G, and B and the liquid crystal display element 2 by AC, the polarities are inverted every vertical period and input to the electrodes of the liquid crystal display element 2 via the X driver 13. . Video chroma processing circuit 11,
The RGB output circuit 12, the X driver 13, and the Y driver 16 are synchronized by the synchronization processing circuit 14 and the controller 15.

In the above embodiment, since one liquid crystal display element is used as the light valve, it is necessary to provide a color filter (not shown) in the liquid crystal display element 6 in the case of color display. It is natural.

Next, specific examples of the polarizer used in the liquid crystal display device of the present invention will be described.

FIG. 2 is a perspective view of the polarizer according to the first embodiment of the present invention.

Reference numeral 5 denotes a polarizer, which is formed by arranging a plurality of elongated convex portions each having a right-angled triangular cross section along the plane of the transparent plate on both sides of a thin transparent plate, and the incident angle of light with respect to the hypotenuse of the convex portion is Brewster. It was set so as to be a corner. Furthermore, a plurality of this polarizer were stacked.

FIG. 3 is a cross-sectional view schematically showing the polarizer to show the operation of the polarizer shown in FIG.

In FIG. 3, 17 is the incident light to the polarizer 5, and 18 and 19 are the emitted lights from the incident plane 20.
8 is S-polarized light and 19 is P-polarized light. 20 is a polarizer 5
Reference numeral 21 denotes an incident surface corresponding to the hypotenuse of the upper convex portion, and reference numeral 21 denotes an exit surface corresponding to the hypotenuse of the convex portion formed on the other surface of the polarizer 5.

In the present invention, the angle between the normal to the incident surface 20 and the incident light is θ, and the refractive index N of the transparent plate used for the polarizer 5 satisfies tan θ = N.

Therefore, since the angle θ becomes the Brewster angle, the S-polarized light 18 perpendicular to the incident surface 20 is partially reflected and partially transmitted, but all the P-polarized light 19 parallel to the incident surface is transmitted. . This light ray is refracted at the incident surface 20 and is incident on the emitting surface 21, but since the incident surface 20 and the emitting surface 21 are parallel, the P-polarized light 19 is emitted at the same angle as the incident light 17.

When a plurality of polarizers 5 are superposed, the S-polarized light 18 is finally reflected by 100% and all the transmitted light becomes P-polarized light 19.

Further, the finer the plurality of right and left triangular triangular elongated projections of the polarizer 5, the thinner the polarizer 5 can be made.

The operation of this embodiment will be described in detail below with reference to FIG.

In FIG. 4, by arranging the light source 2 in the vicinity of the focal position of the reflector 3 (here, a parabolic shape), the light emitted from the reflector 3 becomes a substantially parallel light beam and enters the cold filter 4. Cold filter 4 is infrared,
It has a spectral characteristic of reflecting ultraviolet rays and transmitting only visible light. The light beam emitted from the cold filter 4 is visible light and is incident on the polarizer 5. At this time, the incident light beam 17 is indefinite polarized light, but the S-polarized light 18 is reflected by the hypotenuse incident surface of each elongated triangular convex portion of the polarizer 5, and the P-polarized light 19 is reflected.
Is transmitted, the light emitted from the polarizer 5 becomes P-polarized light. The incident-side polarization plate 7 of the liquid crystal display element 6 is arranged in the direction in which the P-polarized light is transmitted, so that the S-polarized light, which has conventionally been a factor of temperature rise of the incident-side polarization plate, is transmitted to the incident-side polarization plate. Since it is removed by the polarizer of the present invention before being incident, the temperature rise of the incident side polarizing plate is reduced.

FIG. 5 is a perspective view of a polarizer according to the second embodiment of the present invention.

Reference numeral 5 denotes a polarizer, which is formed by arranging a number of elongated convex portions having a right-angled triangular cross section along the plane of the transparent plate on both sides of a thin transparent plate, and the incident angle of light with respect to the hypotenuse of the convex portion is Brewster. It is characterized in that it is provided so as to form a corner, and the convex portion is symmetrical with respect to the center of the transparent plate.

Further, it is characterized in that a plurality of the polarizers are stacked.

In FIG. 6, by providing the light source 2 near the focal position of the reflector 3 (here, a parabolic shape), the light emitted from the reflector 3 becomes a substantially parallel light beam and enters the cold filter 4. The cold filter 4 has a spectral characteristic of reflecting infrared rays and ultraviolet rays and transmitting only visible light. The light beam emitted from the cold filter 4 is visible light and is incident on the polarizer 5. At this time, the incident light beam 17 is indefinite polarized light, but the S-polarized light 18 is reflected by the oblique incident surface of each right-angled triangular elongated convex portion of the polarizer 5, and therefore, with respect to the optical axis of the illumination optical system 1. To the left and right (or up and down).

Since the P-polarized light 19 is transmitted, the light emitted from the polarizer 5 is P-polarized light.

The incident-side polarization plate 7 of the liquid crystal display element 6 is arranged in the direction in which the P-polarized light is transmitted, so that the S-polarized light, which has conventionally been a factor of temperature rise of the incident-side polarization plate, is incident on the incident side. Since it is removed by the polarizer of the present invention before entering the polarizing plate, the temperature rise of the incident side polarizing plate is reduced.

The above embodiment can also be applied to a method using three liquid crystal display elements corresponding to so-called three primary colors (R, G, B). 7th is a schematic block diagram which shows the Example of the projection type liquid crystal display device of this invention.

In FIG. 10, the light source 2 is connected to the reflector 3
The light emitted from the reflector 3 becomes a substantially parallel light beam and is incident on the cold filter 4 by being provided near the focal position (here, a parabolic shape). The cold filter 4 has a spectral characteristic of reflecting infrared rays and ultraviolet rays and transmitting only visible light. The light beam emitted from the cold filter 4 is visible light and is incident on the polarizer 5. At this time, the incident light beam 17 is indefinite polarized light, but the S-polarized light 18 is reflected by the oblique incident surface of each of the right and left triangular triangular elongated projections of the polarizer 5, and the P-polarized light 19 is transmitted. The outgoing light of No. 5 becomes P-polarized light.

Reference numerals 22a and 22b are dichroic mirrors for color separation, 22a is a dichroic mirror for G (green) reflection, and 22b is a dichroic mirror for R (red) reflection. 23a and 23b are total reflection mirrors, 2
4a and 24b are dichroic mirrors for color combination, 24a is a dichroic mirror for R reflection, and 24b.
Is a dichroic mirror for RG reflection.

The P-polarized light 19 is a dichroic mirror 22.
The light is split into G, R, and B (blue) by a. The light beam reflected by the dichroic mirror 22a is a total reflection mirror 23b.
And is incident on the G liquid crystal panel 6a. The light beam transmitted through the dichroic mirror 22a is split into R and B by the dichroic mirror 22b, and the light beam reflected by the dichroic mirror 22b enters the R liquid crystal panel 6b. The light ray transmitted through the dichroic mirror 22b is incident on the B liquid crystal panel 6c.

The incident-side polarization plate 7 of the liquid crystal display elements 6a, 6b, 6c is arranged in the direction in which the P-polarized light is transmitted, and as a result, the S-polarized light, which has conventionally been a factor of increasing the temperature of the incident-side polarization plate. Since the light is removed by the polarizer of the present invention before entering the incident side polarizing plate, the temperature rise of the incident side polarizing plate is reduced.

The light beam emitted from the liquid crystal display element 6a passes through the dichroic mirror 23a and is transmitted through the dichroic mirror 24.
It reflects b and enters the projection lens 9.

The light beam emitted from the liquid crystal display element 6b is reflected by the dichroic mirror 23a and is reflected by the dichroic mirror 24.
It reflects b and enters the projection lens 9.

The light beam emitted from the liquid crystal display element 6c is reflected by the total reflection mirror 23b, transmitted through the dichroic mirror 24b and incident on the projection lens 9.

Here, each liquid crystal display element 6a, 6b, 6c
The light rays that are emitted from the projection lens 6 and are incident on the projection lens 6 have the same optical axis, and the distances from the liquid crystal display elements to the projection lens 9 are the same, so that R, G, and A color enlarged image in which B is combined is obtained.

[0045]

According to the present invention, the light beam emitted from the illuminating device is extracted by the polarizer only the necessary P polarized light and the unnecessary S polarized light is reflected before entering the incident side polarization plate.
Therefore, there is almost no temperature rise of the incident side polarizing plate,
A projection type liquid crystal display device which is highly reliable and compact can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a projection type liquid crystal display device as a first embodiment of the present invention.

FIG. 2 is a perspective view of a polarizer of the present invention.

FIG. 3 is a cross-sectional view showing the operation of the polarizer of the present invention.

FIG. 4 is an explanatory diagram showing an operation of the projection type liquid crystal display device of the present invention.

FIG. 5 is a perspective view of a polarizer of the present invention.

FIG. 6 is an explanatory diagram showing an operation of the projection type liquid crystal display device of the present invention.

FIG. 7 is an explanatory diagram of a projection type liquid crystal display device as a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Illumination device, 2 ... Light source, 3 ... Reflector, 4 ... Cold filter, 5 ... Polarizer, 6 ... Liquid crystal display element, 7 ... Polarizing plate, 8 ... Liquid crystal cell, 9 ... Projection lens, 10 ... Screen, 11 ... Video chroma processing circuit, 12 ... RGB output circuit, 13 ... X driver, 14 ... Synchronous processing circuit, 15 ... Controller, 16 ... Y driver.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inoue Hisao Inage, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd. Inside the Hitachi Media Visual Media Laboratory (72) Inventor Takesuke Maruyama 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd. Visual Media Research Center

Claims (5)

[Claims] 1. A thin transparent plate is formed with a plurality of elongated convex portions each having a right-angled triangular cross section along the plane of the transparent plate, and the incident angle of light with respect to the hypotenuse of the convex portion is the Brewster angle. A polarizer characterized by being provided as follows. 2. A thin transparent plate is formed with a plurality of elongated convex portions each having a right-angled triangular cross-section along the plane of the transparent plate, and the incident angle of light with respect to the hypotenuse of the convex portion is the Brewster angle. The polarizer is characterized in that the convex portion is provided so as to be symmetrical with respect to the center of the transparent plate. 3. A polarizer formed by stacking a plurality of the polarizers according to claim 1 or 2. 4. A lighting device, a liquid crystal display element for displaying an image by transmitting light emitted from the lighting device, and a projection lens for enlarging an image displayed on the liquid crystal display element on a screen. A projection type liquid crystal display device comprising the polarizer according to claim 1, 2 or 3 between the illumination device and the liquid crystal display element. 5. An image is obtained by transmitting an illuminating device, a dichroic mirror for color separation for splitting light emitted from the illuminating device into three primary colors, and light emitted from the dichroic mirror for color separation. A liquid crystal display element for displaying, a color combining dichroic mirror for combining light emitted from the liquid crystal display element 6, and a projection lens for enlarging an image displayed on the liquid crystal display element on a screen, A projection type liquid crystal display device, wherein the polarizer according to claim 1, 2 or 3 is provided between the lighting device and the liquid crystal display element.